Method of hot forging or extruding metal shapes and lubricant for use in hot forging and extruding operations



J 28, 1958 w. M. DICKSON METHOD OF HOT FORGING OR EXTRUDING' METAL SHAPES AND LUBRICANT FOR USE IN HOT FORGING AND EXTRUDING OPERATIONS Filed March 3, 1.955

INVENTOR W||liom M. Dickson MW ATTO R N EYS United 2,821,016 Patented Jan. 28, 1958 fifice NIETHOD OF HOT FORGING OR EXTRUDING METAL SHAPES AND LUBRICANT FOR USE IN HOT FORGIN G AND EXTRUDING OPERATIONS William M. Dickson, Houston, Tex.

Application March 3, 1955, Serial No. 491,957

6 Claims. (Cl. 29-424) My invention relates to improvements in the hot forging of metal articles, and more particularly to the hot forging of steel articles in dies in the presence of a cooling and lubricating solution and to an improved lubricant for use in hot forging or extruding operations.

In high temperature forging operations, as for example in the forging of steel articles or shapes, a number of difficulties have been encountered because of the rapid wear of the dies, even though the billets subjected to forging are previously descaled. One such difiiculty, for example, is the scoring of the dies by the hot metal article or shape when it is forced out of the die. This scoring wears the dies and leaves undesirable score marks on the article or shape and gradually increases the size of the die cavity so that it must be discarded. Other difficulties are caused by the hot metal seizing to a part of the die and causing pitting or breakage.

Various attempts have been made to overcome these.

difficulties by the use of cooling water in and on the dies, but even water or attempts to use oil with water have not avoided the rapid destruction of the dies or eliminated the scoring of the dies and the articles produced therein.

Other difiiculties or problems have also developed because of the wear and erosion of the dies in hot forging operations. For example, in the automatic hot forging of nuts and other articles, the wear of the dies, particularly the die cavity increases the amount of metal which,

must be supplied to the die. However, when additional metal in the form of larger slugs or billets is sent to thev dies, difliculties are encountered in the handling of the slugs because of their increased size, which often results in the misplacing of the slugs with respect to the dies by the transfer mechanism.

It has been discovered that when hot steel at a forging temperature, for example upward of 2,000 E, is pressed into a die, there is some tendency of the hot steel to be welded to the die, which is generally of very hard alloy steel. Even though the hot steel is in the die a very short period of time, repeated operations cause heat check. marks in the dies along with drag or score marks.

The foregoing difficulties cause rapid wear or destruction of the dies and result in unsatisfactory forgings and in making the operation unduly expensive because the.

worn dies must be replaced by new dies before a reasonable number of pieces have been produced.

The primary object, therefore, of my invention is to provide an improved method of hot forging or extruding metal articles by which the die life of the forging dies is' greatly increased.

Another object of my invention is to provide an im-- proved method of hot forging steel articles including an improved method of lubricating and cooling the forging dies.

Another object of my invention is to provide an im-- proved lubricating and cooling medium for use in hightemperature metal forging and extruding operations;

In accordance with my invention, the foregoing and other difficulties are overcome and a greatly extended die life is obtained by carrying out the forging operation in the presence of a lubricating and cooling medium comprising a water solution containing suspended colloidal graphite and a soluble oil, which medium is applied to all parts of the forging equipment engaged by the hot billets or slugs delivered thereto for forging and which are forged therein.

In a preferred form of the improved method, the cooling and lubricating solution is applied directly on and into the forging dies and onto the hot billets or slugs as they are introduced into the dies.

The improved cooling and lubricating solution preferably comprises a water solution containing a relatively small percentage of suspended colloidal graphite and from 1 /2 to about 7% of a soluble oil.

An important function of the solution in the forging operation is its lubricating characteristics which prevent any adherence of the hot metal being forged to the highly polished surfaces of the forging dies. Repeated tests have shown, however, that a water suspension of colloidal graphite alone will not effect the desired lubrication of the forging dies and prevent scoring and other damage. The same is true of a solution of the soluble oil alone in water, in any proportion.

Since the forging operation is carried out at extremely high temperatures, it has so far been impossible to determine how the combination of the soluble oil and colloidal graphite in water functions to give the improved results. One theory which was thought plausible was that the small proportion of soluble oil in the water solution adhered to the colloidal particles of graphite and'was burned on the surface of the hot slugs or billets, or car bonized thereon as molecular carbon to effect a lubricating action between the hot metal being forged and the forging dies. Furthermore, it was considered that to some extent at least there may be a similar molecular deposit or formation of a carbon lubricant on the polished surfaces of the forging dies. The foregoing may account for the gradual loss of soluble oil from the solution.

Regardless of whether or not the foregoing theory or theoretical explanation is correct, the use of the im-i proved cooling and lubricating solution has produced exceptional and unexpected results, which has extended the life of the forging dies five fold or more.

For example, in a particular automatic hot forging operation, where steel articles were produced in forging dies from hot metal slugs, the die life where water was used as the cooling and lubricating medium was only sufficient for the production of about 30,000 forged articles of A. I. S. I. 1045 steel. However, after the discovery of the improved cooling and lubricating solution and its use in the same forging operation with the same type of dies as many as 175,000 forged articles of commercial quality were produced on a single set of dies.

Other features, objects and advantages of the improvements of the present invention are described more in detail hereinafter in connection with the accompanyingdrawing comprising a diagrammatic or schematic view partly in plan and partly in vertical section.

While the features of the invention may be used in connection with various types of hot forging and extruding operations, it will be described and illustrated in connection with its use in the hot forging of steel nut blanks. Referring to the drawing, a round steel bar 10 heated to a bright red temperature of approximately 2300 F. is delivered endwise to a cut-oif station, including a &ed member 12 and a movable cut-01f knife 14, where substantially cylindrical slugs 16 are successively cut from the end of the bar. Each slug is movedfrcnnv the cutting station into a press including a fixed member 18 and' a movable member 20, which reduces the length of the slug and bulges its periphery as shown by the slug 2 If h ho a i oa otl ith s ale. thisw l be substantially all cracked oil the periphery ofthe. slugs as they are-bulged by the movable press member: 20'. The ends'of the slugs will be free of scale, because of the out off. If the bar 10 is'f-ree. of scale,, it is advantageousto press the slugs to approximately. thedesired diameterandthickness for insertion into the cavity 24 of a receiving die 26;

The receiving die 26 with its cavity 24is shaped, for

purposes of illustration, to form the exterior surface of the bulged slug 22 into a hexnut shapein cooperation. with the movable die member 28 and punch 30.; Upon movement. of the die-member28 and punch 30,- the slug 22 is moved into the die cavity=24in opposition tg' a spring biased knock-out pin 32- extending axially through the receiving die 26. The elements 28 and 30 force the plastic metalof the bulged slug into the corners of'the die cavity and form an axial punch hole 33; When the elements 28 and 30 are retracted, theknock-out pin 32. actuated by. a plunger 34,' forces the shaped slug out of the die cavity 24, after which it is moved to a punch-out position to the right where the shaped slug 36 is set over an opening 38 in a punch-out die. A reciprocable punch 40'is: actuated to complete the hole through the axis. of

the shaped; slug to produce a nut blank 42 readyfor threading. As the punch 40 is retracted, the nut blank 42 is stripped therefrom by a fixed retaining: member 44, through which the punch moves.

During the foregoing operations, the. equipment is liters ally flooded with the cooling and lubricating. solution re-. ferred to above. A supply of this solution 50 is. contained in a supply tank 52, preferably located below the surface of the floor 54, on which the. forging. equipment is mounted, As an example, the forging equipment described above may comprise elements of an automatic hot forging machine mounted on the 'fioorsection. 54, o h t all f. th solu i n sp ayedand delivered onto the machine drains onto the floor from which it flows into a s ll t ng nk wh re scale and ther particles re di y settle th s lution hen. flowing over a weir 58 directly into the tank 52.

Solution to be spr y an ooded onto. theforsine. qu p is drawn. from the ta k. throughla pipe 60 by m ans of a p mp 6 op a d by an elect ic motor 4; The motor 64 is at leasta'five horse power n p.togahlmay be a 7 hor po motor for use in. connec ionwith larger forging machines, and the. pump 62 isadapted to deliver a large volume of solution at a pressure of 0, pounds per squar inch thro gh a 1% m2 inch. disrharg pipe 66. and o. ulne tim; bran h pip s 68- and 70, Valveddo i ory shoes 2. e dingfromths hr nohpipos 8. and 0. deli erho olution in regula ed streams onto ll parts o the equipmen used f out ng the-h ghhest d. lug an proooss ngzhemin the orging quipment. F r xample, it. wi l be notedv that stroamsof theso uti n re oode over he elemen s. 12 and 14 and th en por ion of the bar swell. as. the lements 18 and. 2.0,- Fnrthsn ore, th die nd. pun he are tho ghly flooded s h t o ling nd thoro hluhrioation is secured.

I addition to the t eam of solution d liv red thro h h d i ery pips-s7 nto all parts of the forgingequinm and a r l tively l r e. stream f. solut on is delivered from the branch pipe 68 throughra pipe 74 to a sl 76 along the mo a l Pl nger 3 for operatin he nun hutpin T o m mber 3 in ludes a bore uct. 18, wh h. o e ts i h a red du t. 80 in the pin 2; t is a e du b ng-provi ed it a. plural ty f disha outl ts 82;, which. pour stroa s-oft e olution n o he ca ity-z w en h p n, in the position. shown in thedrawine. Ho e ors W onthe pin. is, p .sh. d ba k. so that i s t m s en th ho-bottom of'the die ca ity, heflow is'out off r an ins n bu e en dur ng, t at et leasttwo streams of the solution are flowing toward and into the die cavity 24 as well as onto the slug 22,

die part 28 and punch 30. Throughout the operation the low anofieotive forging temper ure of anp ltim lh 2 10 F. Asia e ampl n t blsnltsore torsstl'ataazra ofiromshoutv 6.0. per minute for 1. /2v inch: nut blanksit about 220 per minute for /8 or %1, inch nut blanks. Even the final stages of forging the nut blanks will have a mperatu e: of around 2 00f F- Qn-the-othoi: han it is an object of the invention to deliver a suflicient quantity of solution to the forging dies and other equipment handling the hot slugs or shapes to maintain their temperature well below 1000 F., preferably not over 700 F.

In making p the solution. 50. f use. inure-process, a ela vely p re water, whi h. s su ntially freeof solids: pre er ly emp oye fPossible, disti odwa er should b used The t nk 5. is a vantage usly designed to. h l about 0 gallons so that an adequa e. vol me of.

l n ys on. hand. Whatever quantity ot o i is made p, approximately one par ofv colloic ah raphi e by Weight is mixed with6..Q Q par sofiwaten. To-

this'nux u o is added pp ximately 2% by o ghtot a, 7

water soluble cutting oil of a well-knowll ypet Such as:

that se as a cuttingo l for t np ng or th eading. A

somewhatlarger. proportion. of colloidal graphite may, be employed, but the relatively small proportion referred tohas been found suflicient. However, the proportion of.

solubleoilmust be within the rangeof'fro n 1 /2. toahout. 7% by-weight; 2% of the soluble oil gives idealrosl s. and is slightly above the minimum requirement so that, there is no danger of having an insuflicient amount present.

The soluble oil being completely or almost complete] lysoluble in water helps tosupport the colloidal graphite.

in a suspended state in the solution. However it is.

visable to provide an agitator, such as the agitator 84." the tank 52 for continuous or intermittent operation to insure a well-mixed solution, although the colloidal graphite in the solutio'n'referred .to has very little, if. any,

fall appreciably below 2% by weight, so thatadditional".

soluble oil can be added if necessary. statedjabove it pp a t a small pr po ti n. fft o ble. oi i u u on the ot. blanks r bfll'otsan l on thesur faces f es. P r a y h diets which m y re: i o mo h a h n so e oft o oth sl nsenlsotthe, o gin qu pm n -1.. e soluble. oil clings. stand :4 p a it he. o loidalsr phite to sense th lll'rlr t r l to clin nd c at he. ie. surfaco .as well as-the hot l gs h p s o le ve a. llLql narti leslottgrsnhit At least a n r of he solub e. oilis bcliovod toh rn or; rh niz n. hes surf ces. and hold he. graphitowthor n- How n. in e e s luble. oil isnrs ont in. sa het.

minute amounts d s not. l a e suflisie t solid ma ter: to be objectionable. 0n the-other hand, and in anycase' it inoreases the lubricating, effect because graphite alone inw ri in fio tive as. a l bri n he he; ininut proportion of soluble oil coating the graphite i a d o ge n h clio or slurs;v tin: conn ng! rat isles f graphit adh re to the. clie-su taces. t orsblt- Pr n ubri ant which" may include any ca es formed from the oil.

It s Possible tha e minu e f oil arrisdfhy he co loi al. raphi e particles arein'some was uring; beatings. carbonized. o the dis surfac s. and. whilst. thereto so as to give a lubricant which permits the free movement of the formed article from the die cavity, or the free withdrawal of punches, such as the punches 3t) and 40 from the hot billet, slug or blank Without the creation of heat marks or scores on the dies or on the surfaces of the formed articles.

In the hot forging and extrusion of slugs or billets in dies, the improved solution of the present invention allows the hot metal to flow freely under pressure to all corners or crevices of the dies with a minimum amount of galling or seizure of the hot metals to the dies.

In making and using the solution, it is very important that the soluble oil ratio not be increased appreciably beyond the proportions given, since a greater proportion of soluble oil, for example, in the solution, reduces the stability of the solution and gives less cooling and lubrication, thereby allowing the dies to become overheated, which results in taking the temper out of the dies, as well as causing the formation of heat check marks, all of which reduces the useful life of the dies.

While extremely finely ground or colloidal graphite from any source may be used in making up the solution, it has been found convenient to utilize an available commercial liquid product containing 10% by weight of colloidal graphite, having the finest particle size dispersed in 1,3-butylene glycol, the liquid product having a density of 8.9 lbs. per gallon. This product is readily diluted or miscible with water and normally sold as a rubber lubricant. Where this dispersion product is used to make up the solution, approximately one part of the graphite dispersion is mixed with 600 parts of water. The solution containing this graphite dispersion and the soluble oil shows no visible tendency to separate or deposit the graphite, but on the other hand, remains substantially uniform for considerable periods of time, so that it is well suited for use in a recirculating system including a relatively large circulating tank and for use over and over again for lubricating and cooling hot dies.

While various soluble cutting oils, known and used generally for use in tapping, threading and other metal cutting operations may be used, it has been found convenient to utilize one of the commercial products sold by various oil companies, for example, the product sold by the Texas Company known as Soluble C, soluble cutting oil. The soluble cutting oils sold by other oil companies may also be used.

The improved cooling and lubricating solution according to the invention may advantageously include a small proportion approximating from 0.05% to 1% of a Wetting agent for increasing the ability of the Water solution to wet metals. Any of the well-known wetting agents may be used for this purpose, which are soluble or readily dispersed in water. In fact, the soluble oil itself greatly increases the Wetting power of water for metals.

The improved solution of the present invention provides an effective medium for lubricating and cooling dies used in high temperature forging and extruding operations. Its unusual and unexpected action is believed to result in providing an almost invisible coating on the die surfaces and the surfaces of the hot metal billets or slugs being forged or extruded. The eifectiveness of the lubricant and method of the invention have been proved in long continuous forging operations at temperatures of from 2100 to 2300 F. and in comparison with other presently used cooling agents and methods.

It is believed that the reason for the ineffectiveness of graphite alone, for example when supplied to hot die surfaces with water, is that the graphite has no tendency to wet or adhere to the die surfaces but may, in fact, run off or be squeezed out along with the water.

I claim:

1. In the hot forging of steel articles from heated steel bar stock in which the steel bar stock is heated to a temperature approximating 2300 F., slugs are cut successively from one end of the heated steel bar stock by a cut-off means, the slugs being placed in succession in a die cavity of a forming die and pressed therein to the shape of the steel article, the improvement in which a cooling and lubricating composition is flooded over the slugs as they are cut from the bar stock, the cut-off means and all parts of the forming die during the cutting of the slugs and the forming of the steel articles therefrom, said cooling and lubricating composition comprising a water solution consisting essentially of water, approximately one part by weight of finely-divided graphite to 6000 parts by weight of water, and from approximately 1.5 to 7% by weightof a soluble cutting oil, whereby scoring and excessive Wear of the forming die is prevented.

2. The improvement as claimed in claim 1, including the provision of a body of the cooling and lubricating composition, continuously passing the composition from the body to the cut-off means and die, returning the composition after flooding the cut-0E means and die to the body of the composition for recirculation.

3. In the hot forging of steel articles from heated steel bar stock in which the steel bar stock is heated to a temperature of from 2000 to 2300 F., slugs are cut successively from one end of the heated steel bar stock by a cut-01f means, the hot steel slugs being placed in succession in a die cavity of a forming die and pressed therein to the shape of the die, the improvement in which a cooling and lubricating composition is flooded over the slugs as they are cut from the bar stock, the cut-01f means and all parts of the forming die during the cutting of the slugs and the forming of the steel articles there from, said cooling and lubricating composition comprising a water solution consisting essentially of water initially substantially free of solids, approximately one part by weight of finely-divided graphite in suspension to 6000 parts by weight of water, and approximately 2% by weight of a soluble cutting oil, whereby scoring and excessive wear of the forming die is prevented.

4. A fiuid cooling and lubricating composition for cooling and lubricating the dies during the hot forging or extruding of hot metal billets or slugs in the dies, said composition consisting essentially of water, approximately one part by weight of a mixture composed of 10 parts of colloidal graphite and parts of 1,3 butylene glycol to 600 parts by weight of water, and from about 1.5 to approximately 5% of a soluble cutting oil.

5. A fluid cooling and lubricating composition for cooling and lubricating dies during the hot forging or extruding of hot metal billets or slugs in the dies, said composition consisting essentially of a fluid aqueous mixture containing approximately one part of colloidal graphite to approximately 6000 parts by weight of water, and from approximately 1.5 to 7% by weight of a soluble cutting oil.

6. A composition as claimed in claim 5, including a small proportion of a metal wetting agent.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN THE HOT FORGING OF STEEL ARTICLES FROM HEATED STEEL BAR STOCK IN WHICH THE STEEL BAR STOCK IS HEATED TO A TEMPERATURE APPROXIMATING 2300*F., SLUGS ARE CUT SUCCESSIVELY FROM ONE END OF THE HEATED STEEL BAR STOCK BY A CUT-OFF MEANS, THE SLUGS BEING PLACED IN SUCCESSION IN A DIE CAVITY OF A FORMING DIE AND PRESSED THEREIN TO THE SHAPE OF THE STEEL ARTICLE, THE IMPROVEMENT IN WHICH A COOLING AND LUBRICATING COMPOSITION IS FLOODED OVER THE SLUGS AS THEY ARE CUT FROM THE BAR STOCK, THE CUT-OFF MEANS AND ALL PARTS OF THE FORMING DIE DURING THE CUTTING OF THE SLUGS AND THE FORMING OF THE STEEL ARTICLES THEREFROM, SAID COOLING AND LUBRICATING COMPOSITION COMPRISING A WATER SOLUTION CONSISTING ESSENTIALLY OF WATER, APPROXIMATELY ONE PART BY WEIGHT OF FINELY-DIVIDED GRAPHITE TO 6000 PARTS BY WEIGHT OF FINELY-DIVIDED GRAPHITE 1.5 TO 7% BY WEIGHT OF SOLUBLE CUTTING OIL, WHEREBY SCORING AND EXCESSIVE WEAR OF THE FORMING DIE IS PREVENTED. 